Analysis of Slurry and Fixed Abrasive Diamond Wire Sawn Silicon Wafers

HaoWu, Kevin Skenes, Chris Yang, Frank Mess, Shreyes N. Melkote, Steven DanylukG. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA

o T2, T3 thicker than T1

o T4 thicker than T2, T3

o Edges 3, 4 thicker than 1 and 2

VAS2 wafer (nominal thickness 180µm) thickness variation

� Surface morphologies of slurry and diamond cut wafers are

quite different.

� Slurry sawn wafers have characteristic patterns of wafer

thickness and surface roughness; may be due to a reduction in

cutting grit size due to fission in the cutting process.

� Slurry sawn wafers have lower crack density but larger

microcrack length.

� Fracture strength of diamond cut wafers is comparable or

superior to slurry cut wafers.

� Occurrence of a-Si in area of diamond cut wafers exhibiting ductile

mode cutting

� Rare occurrence of a-Si in slurry cut wafers

Objective

Results

Slurry Sawing

A. Surface Morphology

Conclusions

Acknowledgements

� Quantitatively analyze and compare characteristics of

silicon wafers sliced by loose abrasive slurry sawing and

fixed abrasive diamond wire sawing

Diamond Wire Sawing

Silicon wafers tested

Slu

rry

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Wire S

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B. Phase Analysis

C. Thickness Variation in Slurry Cut Wafers

D. Surface Roughness Variation

E. Wafer Surface Profile

� Diamond cut wafers have larger variation than slurry cut wafers

� Thickness almost constant

F. Residual Stress Analysis

Slu

rry

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Wire S

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Max. shear stress in VAS1 and

VAS2 group: 1.5-3.3MPa

Max. shear stress in VAD group:

2.4 MPa

G. Microcracks

H. Fracture Strength

Wafer edge crack measurement summary

Weibull plot for four line bendingSurface roughness decreases along wire direction in slurry cut wafers

� Financial and in-kind support of the NSF Silicon Solar

Consortium (SiSoC)21st Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes